Throughout the Popoya Islands community pressure is exerted on people who win the national lottery to share their good fortune with their neighbors.
Given that ...
Throughout the whole country, people who win the lottery receive pressure from their community to share their good fortune with their neighbors.
How can it be that ...
In rural areas the winner often throws an elaborate feast, which wipes out all their winnings, whereas in the cities, winners often use their winning for their own personal investments.
Evaluate / Goal
We need something that's different about winning in a rural area vs. winning in a city area that could explain why the city folk seem to get away defying the community pressure to share the winnings.
(For example, maybe in a rural area, you know everyone and see everyone, so the community pressure is a lot stronger on you than if you live in the city)